The exclusion of an abdominal aortic aneurysm (AAA) by placement of an intraluminal, stent-anchored, Dacron prosthetic graft retrograde from the femoral artery is vastly different from the open conventional Dacron repair, and this approach has galvanized vascular surgeons worldwide. Although stent grafts were performed in Russia in the 1980s, Parodi1 first described his technique in 1991. The first endovascular aortic graft performed in the United States was reported in May 1995.2 Eleven years later, we have learned a great deal about the aneurysm, the endograft, and the outcome of the new procedure. The key lessons are in accurate measurement of the aneurysm, careful patient selection, selection of an appropriate device, device placement, management of endoleaks, and long-term outcome.
The risk for AAA rupture is related to its maximum diameter. Rupture occurs when the wall stress exceeds the tensile strength of the aortic wall. Maximum diameters >5 cm, recent rapid growth, or pain are indications of a need for repair. Rupture of the aorta is associated with a high mortality. A longitudinal population screening study of 41,000 males in West Australia showed no definite benefit from ultrasound screening to detect abdominal aortic aneurysm. There was, however, some benefit in selected groups of men suitable for endografts between the ages of 65 and 75, provided that the rate of open operation was low.3 In contrast, in the United Kingdom, screening once on 62-year-old men was shown to detect the 15% of men with disease, which enabled longitudinal follow-up of this group and reduced the rupture rate.4 An AAA is often detected as a result of abdominal ultrasound or computed tomographic (CT) examinations for other conditions.
Angiography with a graduated catheter was once a prerequisite for assessment for endografting, but, as a result of improvements in CT, preoperative planning is now largely performed by multislice CT with 3-dimensional and
maximum-intensity projection reconstructions. A typical CT protocol is listed in Table 1 and Figure 1.
The most critical measurement is the length of the upper aneurysm neck. Ideally, the neck should be >15 mm in length, <30 mm in diameter, cylindrical in shape, and free of plaque without excessive tortuosity. The aim of measurement is to determine the size and length of endograft that is required. Modular bifurcated endografts have made the selection of the correct overall length much less of a problem, as they can be overlapped to create an adjustable overall length in situ.
Currently, angiography has a more limited role in patients with tortuous aortas or in those in whom other procedures, such as lumbar or iliac embolization, are required. Embolization of large lumbar arteries is often considered to reduce the opportunity for type II endoleaks, and there is evidence that embolization of a patent inferior mesenteric artery prior to placement of an endograft is associated with a lower incidence of endoleak and a more rapid decrease in aneurysm size.5 When the aneurysm sac has a low thrombus load, there appears to be more opportunity for connections to persist across the excluded sac between lumbar arteries and the inferior mesenteric artery.